Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An imaging device includes an operation unit that instructs an operation
by operation input, an imaging control unit that controls an operation of
an imaging unit having a first imaging element, a counting unit that
counts the number of generation times of the vertical synchronization
signal, and a control unit that calculates the number of generation times
of the vertical synchronization signal inserted between second processing
frames based on a difference value between the number of generation times
of the vertical synchronization signal generated by a second imaging
element of the other imaging device and inserted between the second
processing frames and the number of generation times of the vertical
synchronization signal inserted between first processing frames, so as to
notify the other imaging device of timing to start an instructed
operation and an instruction, and perform the notified operation after
elapse of a predetermined period.

Claims:

1. An imaging device, comprising: an operation unit configured to
instruct an operation by operation input; an imaging control unit
configured to control an operation of an imaging unit having a first
imaging element that outputs a video signal in a first processing frame
for every vertical synchronization signal that is inserted between first
processing frames, by incident light of a subject incident through a
lens; a counting unit configured to count a number of generation times of
the vertical synchronization signal generated by the first imaging
element; and a control unit that calculates a number of generation times
of the vertical synchronization signal that is inserted between second
processing frames based on a difference value between a number of
generation times, the number of generation times being notified from the
other imaging device, of the vertical synchronization signal that is
generated by a second imaging element included in the other imaging
device, the other imaging device being connected by a control line that
transmits a control signal, and inserted between the second processing
frames and a number of generation times of the vertical synchronization
signal that is inserted between the first processing frames, so as to
notify the other imaging device of timing at which the other imaging
device starts an instructed operation after elapse of a predetermined
period and an instruction given by the operation input, based on the
number of generation times of the vertical synchronization signal that is
inserted between the second processing frames, and perform the operation
that is notified of after the elapse of the predetermined period from a
time point on which the operation input is performed.

2. The imaging device according to claim 1, wherein the counting unit
counts a number of generation times of the vertical synchronization
signal that is generated by the first imaging element as a frame number
of the first processing frames, and the control unit notifies the other
imaging device of a frame number obtained by adding a plurality of frame
periods to a frame number of the second processing frames, the frame
number of the second processing frames being calculated when a difference
value between a frame number of the second processing frames received
from the other imaging device every time the second imaging element
generates the vertical synchronization signal and a frame number of the
first processing frames is constant for the plurality of frame periods,
as timing at which the other imaging device starts an operation, in a
case where timing on which a vertical synchronization signal of the first
processing frame is generated and timing on which a vertical
synchronization signal of the second processing frame is generated are
preliminarily matched with each other and the other imaging device counts
the number of generation times of the vertical synchronization signal
inserted between the second processing frames as the frame number of the
second processing frames.

3. The imaging device according to claim 2, wherein when it is difficult
for the control unit to notify the other imaging device of the frame
number of the first processing frames within a period of the first
processing frame or to receive the frame number of the second processing
frames from the other imaging device within the period of the first
processing frame, the control unit notifies the other imaging device of
the frame number of the first processing frames or receives the frame
number of the second processing frames from the other imaging device over
a frame period following the first processing frame.

4. The imaging device according to claim 3, wherein when the control unit
obtains a second difference value, the second difference value being
different from the difference value obtained over predetermined times or
more, over less than the predetermined times, the control unit discards
the second difference value.

5. The imaging device according to claim 4, wherein an operation
instructed by the operation input of the operation unit includes one of
start and stop of imaging and the first and second processing frames
include one of an imaging frame and a reproduction frame.

6. A synchronization control method, comprising: instructing an operation
by operation input; controlling an operation of an imaging unit having a
first imaging element that outputs a video signal in a first processing
frame for every vertical synchronization signal that is inserted between
first processing frames, by incident light of a subject incident through
a lens; counting a number of generation times of the vertical
synchronization signal generated by the first imaging element; and
calculating a number of generation times of the vertical synchronization
signal that is inserted between second processing frames based on a
difference value between a number of generation times, the number of
generation times being notified from the other imaging device, of the
vertical synchronization signal that is generated by a second imaging
element included in the other imaging device, the other imaging device
being connected by a control line that transmits a control signal, and
inserted between the second processing frames and a number of generation
times of the vertical synchronization signal that is inserted between the
first processing frames, so as to notify the other imaging device of
timing at which the other imaging device starts an instructed operation
after elapse of a predetermined period and an instruction given by the
operation input, based on the number of generation times of the vertical
synchronization signal that is inserted between the second processing
frames, and perform the operation that is notified of after the elapse of
the predetermined period from a time point on which the operation input
is performed.

7. A reproduction device, comprising: an operation unit configured to
instruct an operation by operation input; a counting unit configured to
count a number of generation times of a vertical synchronization signal
that is inserted between first processing frames of a video signal that
is read out from a recording unit and reproduced; and a control unit that
calculates a number of generation times of the vertical synchronization
signal that is inserted between second processing frames based on a
difference value between a number of generation times, the number of
generation times being notified from the other reproduction device, of
the vertical synchronization signal that is generated by an imaging
element included in the other reproduction device, the other reproduction
device being connected by a control line that transmits a control signal,
and inserted between the second processing frames and a number of
generation times of the vertical synchronization signal that is inserted
between the first processing frames, so as to notify the other
reproduction device of timing at which the other reproduction device
starts an instructed operation after elapse of a predetermined period and
an instruction given by the operation input, based on the number of
generation times of the vertical synchronization signal that is inserted
between the second processing frames, and perform the operation that is
notified of after the elapse of the predetermined period from a time
point on which the operation input is performed.

8. A stereoscopic video imaging system, comprising: a first imaging
device; and a second imaging device; wherein the first imaging device
includes a first operation unit configured to instruct an operation by
operation input, a first imaging control unit configured to control an
operation of an imaging unit having a first imaging element that outputs
a video signal in a first processing frame for every vertical
synchronization signal that is inserted between first processing frames,
by incident light of a subject incident through a lens, a first counting
unit configured to count a number of generation times of the vertical
synchronization signal generated by the first imaging element, and a
first control unit that calculates a number of generation times of the
vertical synchronization signal that is inserted between second
processing frames based on a difference value between a number of
generation times, the number of generation times being notified from the
second imaging device, of the vertical synchronization signal that is
generated by a second imaging element included in the second imaging
device, the second imaging device being connected by a control line that
transmits a control signal, and inserted between the second processing
frames and a number of generation times of the vertical synchronization
signal that is insetted between the first processing frames, so as to
notify the second imaging device of timing at which the second imaging
device starts an instructed operation after elapse of a predetermined
period and an instruction given by the operation input, based on the
number of generation times of the vertical synchronization signal that is
inserted between the second processing frames, and perform the operation
that is notified of after the elapse of the predetermined period from a
time point on which the operation input is performed; and the second
imaging device includes a second imaging control unit configured to
control an operation of a second imaging unit having a second imaging
element that outputs a video signal in a second processing frame for
every vertical synchronization signal that is inserted between second
processing frames, by incident light of a subject incident through a
lens, a second counting unit configured to count a number of generation
times of the vertical synchronization signal generated by the second
imaging element, and a second control unit configured to notify the first
imaging device of the number of generation times of the vertical
synchronization signal inserted between the second processing frames and
perform an instructed operation after elapse of a predetermined period
from a time point on which the operation input is performed, based on
timing on which the instructed operation is started after the elapse of
the predetermined period and an instruction given by the operation input,
the timing and the instruction being received from the first imaging
device.

Description:

BACKGROUND

[0001] The present disclosure relates to an imaging device, a
synchronization control method, a reproduction device, and a stereoscopic
video imaging system that are preferable to be applied to a case where a
stereoscopic video image (3D video image) is generated from video images
picked up by two cameras, for example.

[0002] In related art, there is a technique to generate a stereoscopic
video image (3D video image) which can be three-dimensionally viewed by a
user, by using video images of a same subject picked up by two cameras
which are disposed in a manner to correspond to parallax of right and
left eyes of the user. In order to pick up a stereoscopic video image,
start or stop of video recording or start or stop of video reproduction
(referred to below as merely "start or stop of processing") is performed
in a manner to synchronize operations of two cameras.

[0003] Japanese Unexamined Patent Application Publication No. 2006-163640
discloses such technique that a plurality of video tape recorders are
connected to a video camera in series and a first connector to which a
recording signal is transmitted and a second connector to which return of
a state confirmation signal is transmitted are bidirectionally connected.

SUMMARY

[0004] By the way, a stereoscopic video imaging system of related art has
not had a linkage function by which two cameras control mutual
operations. Therefore, even though a user performs operation input with
respect to each of two cameras, it has been difficult for the two cameras
to simultaneously perform start or stop of processing due to mismatch of
timings of the operation input. Here, if timings of start or stop of
processing performed by two cameras, that is, processing frames of video
signals which are picked up or reproduced by respective cameras are not
exactly matched, feeling of strangeness is generated in a video image
which is reproduced and three-dimensionally viewed, generating an
imperfect video image. Therefore, start or stop timings of processing
frames have had to be separately matched by using a time code or the like
attached to respective clip files generated by two cameras.

[0005] Further, above-mentioned Japanese Unexamined Patent Application
Publication No. 2006-163640 discloses the technique to continuously
perform processing while making the plurality of video tape recorders
confirm states. However, this technique is employed only in a case where
video tape recorders are operated in conjunction with each other.
Accordingly, in a case where two cameras are used so as to pick up
stereoscopic video images, it is not Considered to rigorously control
record or reproduction of a video image.

[0006] It is desirable to accurately match timings of processing when
stereoscopic video images are processed by using two imaging devices.

[0007] An imaging device according to an embodiment of the present
disclosure instructs an operation by operation input and controls an
operation of an imaging unit having a first imaging element that outputs
a video signal in a first processing frame for every vertical
synchronization signal which is inserted between first processing frames,
by incident light of a subject incident through a lens. Further, the
imaging device counts the number of generation times of the vertical
synchronization signal generated by the imaging element as the frame
number of the first processing frames. Further, the imaging device
obtains the number of generation times, which is notified from the other
imaging device, of the vertical synchronization signal that is generated
by a second imaging element of the other imaging device, which is
connected to the imaging device by a control line that transmits a
control signal, and are inserted between second processing frames. Here,
the imaging device calculates the number of generation times of the
vertical synchronization signal that is inserted between second
processing frames based on a difference value between the generation
number of vertical synchronization signals that are inserted between
second processing frames and the number of generation times of the
vertical synchronization signal that is inserted between the first
processing frames. Then, the imaging device notifies the other imaging
device of timing at which the other imaging device starts an instructed
operation after elapse of a predetermined period and an instruction given
by the operation input, based on the number of generation times of the
vertical synchronization signal inserted between the second processing
frames. Further, the imaging device performs the operation that is
notified of after the elapse of the predetermined period from a time
point on which the operation input is performed.

[0008] Accordingly, it has become possible to give instruction by
operation input at timing on which instructed operation is started after
elapse of a predetermined period between two imaging devices.

[0009] According to the embodiment of the present disclosure, a first
imaging device notifies the other imaging device of timing on which the
other imaging device starts an instructed operation after elapse of a
predetermined period and an instruction given by operation input, and
performs the notified operation after elapse of the predetermined period
from a time point on which the operation input is performed. Accordingly,
an operation instructed by operation input can be simultaneously
performed and accuracy of start or stop of processing can be enhanced
when a stereoscopic video image is processed by using two imaging
devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a block diagram illustrating an external configuration
example of a stereoscopic video imaging system according to an embodiment
of the present disclosure;

[0011]FIG. 2 is a block diagram illustrating an internal configuration
example of the stereoscopic video imaging system according to the
embodiment of the present disclosure;

[0012] FIGS. 3A to 3C are timing diagrams illustrating examples that a
first camera and a second camera mutually control timings of processing
operations in the embodiment of the present disclosure;

[0013] FIG. 4 is a flowchart illustrating an example of processing of the
first camera in the embodiment of the present disclosure;

[0014]FIG. 5 is a flowchart illustrating an example of processing, which
is performed by a synchronization control unit, of an interface of a
camera control unit in the embodiment of the present disclosure;

[0015]FIG. 6 is a flowchart illustrating an example of processing, which
is performed by the synchronization control unit, of an interface of a
user interface control unit in the embodiment of the present disclosure;
and

[0016] FIG. 7 is a flowchart illustrating an example of processing, which
is performed by the synchronization control unit, of an interface of a
transmission/reception control unit in the embodiment of the present
disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0017] An embodiment of the present disclosure (referred to below as an
embodiment) will be described below. The description will be given in the
following order.

1. Embodiment. (Synchronization Control of Two Cameras: Example of
Stereoscopic Video Imaging System)

2. Modification

1. Embodiment

Example of Synchronization Control of Two Cameras

[0018] An embodiment of the present disclosure is now described with
reference to the accompanying drawings. In this embodiment, a
stereoscopic video imaging system 10 which picks up stereoscopic video
images in a manner to synchronize timings of start or stop of processing
of two cameras (imaging devices) is described as an example (referred to
below as "this example"). The stereoscopic video imaging system 10
employs a synchronization control method for controlling synchronization
of start or stop of processing of two cameras.

[0020] The stereoscopic video imaging system 10 includes a first camera 1
and a second camera 2 as imaging devices which pick up two-dimensional
video images having the same picture size in one second in the same
number of frames. The first camera 1 and the second camera 2 are provided
with common line terminals. The first camera 1 and the second camera 2
can transmit/receive a synchronization control signal which is used for
controlling to synchronize processing of record or reproduction of mutual
video images in a frame unit, while putting the synchronization control
signal in a communication packet by a synchronization control line 3
which is connected to the line terminals and capable of serial
communication.

[0021] The first camera 1 and the second camera 2 include an operation
unit 11 by which a user instructs each unit about an operation by
operation input. As the operation unit 11, an operation switch (a
recording button, a reproducing button, and the like) on the camera body,
a remote controller which is not shown, a push button, a toggle switch, a
touch panel display, and the like, for example, are used.

[0022] The stereoscopic video imaging system 10 further includes a signal
converting device 4 which converts video signals inputted from the first
camera 1 and the second camera 2 into a stereoscopic video signal. The
signal converting device 4 outputs a two-dimensional or three-dimensional
video signal to a display device 5 which is capable of displaying video
images two-dimensionally or three-dimensionally.

[0023] The signal converting device 4 receives an electric to electric
mode (EE) video signal or a Play video signal from the first camera 1 and
the second camera 2. The EE video signal is a signal for instructing the
display device 5 to display a two-dimensional video signal which is
picked up by the first camera 1 and the second camera 2, as a
two-dimensional video image directly. That is, the EE video signal is a
video signal which is outputted by the first camera 1 and the second
camera 2 and directly taken out, as an output with respect to the display
device 5, without going through a recording unit such as HDD. The Play
video signal is a signal for instructing the display device 5 to display
two-dimensional video signals which are reproduced by the first camera 1
and the second camera 2 as a three-dimensional video image.

[0024] The signal converting device 4 outputs a communication packet which
is obtained by combining two-dimensional video signals inputted from the
first camera 1 and the second camera 2 as one three-dimensional video
signal, to the display device 5. When the display device 5 is set in a
two-dimensional display mode in which a two-dimensional video image is
displayed, the display device 5 selects a video signal from video signals
inputted from the first camera 1 and the second camera 2 and displays the
selected video image selected from right and left video images as a
two-dimensional video image. On the other hand, when the display device 5
is set in a three-dimensional display mode in which a three-dimensional
video image is displayed, the display device 5 displays the video signals
as a three-dimensional video image.

[0025] The first camera 1 and the second camera 2 are put on a putting
table (RIG) 6 in stereoscopic video image pick up. Commonly, zoom
magnification of the first camera 1 and the second camera 2 is set to be
unmagnified and the first camera 1 and the second camera 2 are disposed
so that an interval between lenses thereof corresponds to human eyes. A
stereoscopic video image obtained by combining two-dimensional video
images picked up in this state can be visually recognized as a natural
stereoscopic object by a user.

[0026] However, when the first camera 1 and the second camera 2 having
large casings are aligned in a horizontal direction, a subject is taken
with larger parallax than the interval of human eyes, resulting in user's
uncomfortable feeling with respect to a stereoscopic video image that the
user visually recognizes. Therefore, the first camera 1 and the second
camera 2 are disposed on the putting table 6 provided with a half mirror
7. Here, the first camera 1 is disposed on a position on which image
light of a subject is directly incident via the half mirror 7 and the
second camera 2 is disposed on a position on which the image light of the
subject is reflected by the half mirror 7 to be incident. Accordingly,
the first camera 1 and the second camera 2 are disposed so that optical
axes of lenses of the first camera 1 and the second camera 2 intersect
orthogonally.

[0028] The first camera 1 and the second camera 2 have the same function
blocks as each other. Therefore, in the following description, an
internal configuration example of the first camera 1 is described. In the
following description, in order to describe processing of the first
camera 1, the first camera 1 may be referred to as "own device" and the
second camera 2 may be referred to as "the other device".

[0029] The first camera 1 includes a user interface control unit 12 which
receives operation input from the operation unit 11, a camera control
unit 13 which controls an imaging operation, and a RAM 14. The user
interface control unit 12 displays a graphical user interface (GUI) on a
screen when the operation unit 11 is a touch panel display. The first
camera 1 further includes a reproduction control unit 15 which controls
reproduction of a video image recorded in a recording unit which is not
shown and a record control unit 16 which performs control when a video
image is recorded in the recording unit. The first camera 1 further
includes a synchronization control unit 17 which controls an operation of
the second camera 2 so that an imaging operation and reproduction or
record of a video image are performed in synchronization with processing
of the second camera 2. The first camera 1 further includes a RAM 18
which stores various counter values and a transmission/reception control
unit 19 which controls transmission/reception of a communication packet
transmitting through the synchronization control line 3.

[0030] The user interface control unit 12 performs processing of receiving
operation input performed with a button which is not shown and provided
to the operation unit 11, processing of receiving operation input
received from a remote controller which is not shown, and processing of
receiving operation input performed with a remote such as wireless LAN.
The user interface control unit 12 processes an instruction and the like
given by operation input inputted from the graphical user interface such
as a touch panel and performs processing to display various menus and
messages on a touch panel display or the like. Further, the user
interface control unit 12 notifies the synchronization control unit 17 of
the instruction given by the operation input received from the operation
unit 11.

[0031] The camera control unit 13 is used as an imaging control unit which
controls an operation of an imaging unit having a first imaging element
which is not shown and outputs a video signal in the first processing
frame for every vertical synchronization signal which is inserted between
first processing frames, by incident light of a subject incident through
a lens which is not shown. The second camera 2 includes an imaging unit
having a second imaging element. The camera control unit 13 controls an
imaging element such as a complementary metal oxide semiconductor (CMOS)
image sensor which is not shown, a video image processing processor, and
drive of an optical system driving unit including a lens and the like.
The camera control unit 13 corrects a video signal outputted by the
imaging element, in a pixel unit and performs control of auto focusing
processing, auto white balance processing, and the like with respect to
the optical system driving unit.

[0032] Into the RAM 14, a vertical synchronization signal counter 20 which
counts the number of generation times of a vertical synchronization
signal for each frame obtained from the camera control unit 13 writes a
vertical synchronization signal counter value which is used as the frame
number of processing frames. The vertical synchronization signal counter
20 is used as a counting unit which counts the number of generation times
of the vertical synchronization signal generated by the imaging element
as the frame number of the first processing frames. The vertical
synchronization signal counter 20 counts the number of vertical
synchronization signals interrupting from the imaging element that the
camera control unit 13 controls in imaging, and the RAM 14 stores the
number of vertical synchronization signals written by the vertical
synchronization signal counter 20.

[0033] The reproduction control unit 15 performs control of access
processing such as writing and reading of a clip file with respect to a
recording medium which is not shown, control of processing of clip
information, control of decoding processing of the clip file, and the
like. The first camera 1 administrates a video file including a video
signal which is picked up from start to stop of one recording, by a unit
of "clip"; writing and reading with respect to a recording medium can be
performed to every clip file. The record control unit 16 performs control
of access processing with respect to a recording medium, control of
generation processing of a clip file, control of salvage processing to
salvage a discarded clip file, control of encode processing of a video
signal, and the like.

[0034] The synchronization control unit 17 performs following notification
to the second camera 2. The second camera 2 is the other imaging device
which is connected by the synchronization control line 3 which transmits
a control signal. The synchronization control unit 17 receives the number
of generation times, which is notified from the second camera 2, of the
vertical synchronization signal which is generated by a second imaging
element of the second camera 2 and is inserted between second processing
frames. The synchronization control unit 17 calculates the number of
generation times of the vertical synchronization signal inserted between
second processing frames, based on a difference value with respect to the
number of generation times of the vertical synchronization signal
inserted between the first processing frames. Further, the
synchronization control unit 17 notifies the second camera 2 of timing on
which the second camera 2 starts an instructed operation after elapse of
predetermined period and an instruction given by operation input based on
the number of generation times of the vertical synchronization signal
inserted between the second frames. At this time, the first camera 1
performs an instructed operation after elapse of the predetermined period
from a time point on which the operation input is performed.

[0035] The synchronization control unit 17 preliminarily matches timing on
which a vertical synchronization signal of the first processing frame is
generated and timing on which a vertical synchronization signal of the
second processing frame is generated. Here, the second camera 2 counts
the number of generation times of the vertical synchronization signal
inserted between the second processing frames as the frame number of the
second processing frames. At this time, the synchronization control unit
17 determines whether a difference value of the frame number calculated
by using the frame number of the second processing frames received from
the second camera 2 and the frame number of the first processing frames
is constant for a plurality of frame periods, every time the second
imaging element generates a vertical synchronization signal. When the
difference value is constant for the plurality of frame periods, the
synchronization control unit 17 notifies the second camera 2 of the frame
number obtained by adding the plurality of frame periods to the
calculated frame number of the second processing frames as timing on
which the second camera 2 starts an operation. By such control, the first
camera 1 controls timing on which the second camera 2 starts an
instructed operation. Here, the "operation instructed" by operation input
of the operation unit 11 includes imaging start or stop or video
reproduction start or stop, and the first and second processing frames
include an imaging frame or a reproduction frame.

[0036] Thus, the synchronization control unit 17 obtains difference
between counter values of vertical synchronization signals of the first
camera 1 and the second camera 2 and performs control of synchronizing
timing of operation instruction with the second camera 2. Though detailed
processing of the synchronization control unit 17 will be described
later, all processing shown in flowcharts of FIGS. 4 to 7 is performed by
the synchronization control unit 17.

[0037] Further, the synchronization control unit 17 has an interface for
transmitting/receiving data with respect to the camera control unit 13
and performs transmission/reception control unit interface processing
with respect to the transmission/reception control unit 19. This
processing is performed by a module handling an interface with respect to
the transmission/reception control unit 19. The RAM 18 stores counter
values of vertical synchronization signals which are mutually received by
the first camera 1 and the second camera 2, operation instruction
performed by the first camera 1, a counter value of a vertical
synchronization signal which is a trigger of start of operation
instruction, and the like.

[0038] The transmission/reception control unit 19 performs transmission
reception processing of a communication packet, processing of
transmitting a communication packet to the second camera 2, processing of
converting a communication packet in accordance with a specified
communication protocol, processing of controlling a communication device
including a line terminal and the like, and so forth. The synchronization
control unit 17 calculates start timing (based on the number of
generation times of the vertical synchronization signal counter value in
this example) of a processing frame which is executed to synchronize
timings of start or stop of processing. Then, the transmission/reception
control unit 19 requests to transmit control data for instructing the
second camera 2 on an operation to be performed and the processing frame
number, to the second camera 2.

[0039] The first camera 1 preliminarily synchronizes a processing frame of
the first camera 1 and a processing frame of the second camera 2 by
performing genlock with respect to the second camera 2. This
synchronization is performed on generating timing of a vertical
synchronization signal and the synchronization control unit 17 controls
such that a mismatching amount of the synchronization timings is within
time of approximately one line. In this example, control based on a
master-servant relationship in which the first camera 1 is set to be a
main device and the second camera 2 is set to be a sub device is
performed, and synchronization of a processing frame of the second camera
2 is controlled to be matched with a processing frame of the first camera
1 in accordance with an instruction of the first camera 1.

[0040] As described above, start timing of the processing frame of the
first camera 1 and start timing of the processing frame of the second
camera 2 are synchronized with each other by genlock. Then, the first
camera 1 and the second camera 2 detect a difference value of vertical
synchronization signal counter values respectively counted by software
programs operating in respective cameras. Here, a vertical
synchronization signal is generated at timing on which a processing frame
starts, and the synchronization control unit 17 of the first camera 1
figures out the frame number of processing frames in which the second
camera 2 operates, based on the difference value. Accordingly, when the
first camera 1 which is the main device receives operation instruction
which is used for performing start or stop of processing and given by
operation input of a user, the first camera 1 controls an operation of
the second camera 2 so as to make the second camera 2 perform start or
stop of processing simultaneously with the first camera 1. Thus, the
first camera 1 performs synchronization control by which timing of
processing of the second camera 2 is matched with every frame which is
timing of processing of the first camera 1.

[0041] A communication packet transmitted between the cameras is composed
of "K field (4 bytes)" representing a command type, "L field (4 bytes)"
representing a data length, and "V field (maximum 64 bytes)" representing
a data content. In the K field, data for instructing synchronization is
stored, and in the V field, data content representing start or stop of
processing of own device is stored. For example, when data representing a
notice of a vertical synchronization signal counter value is included in
the K field, a vertical synchronization signal counter value of own
device is included in the V field. Further, when information notifying of
format of a clip file is included in the K field, information
representing a picture size of a video image, a frame rate, and a bit
rate is included in the V field.

[0042] By transmitting/receiving a communication packet via the
synchronization control line 3, the first camera 1 and the second camera
2 controlled by the software program can perform processing in a
mutually-synchronized manner for every frame. Therefore, processing to
simultaneously perform an operation to start or stop recording of video
images picked up at the same timing for every frame, and processing to
simultaneously reproduce or stop a content of the same format for every
frame are enabled.

[0043] Here, the first camera 1 and the second camera 2 are used also as
reproduction devices which reproduce a video image in a synchronized
manner. In this case, the second camera 2 is used as the other
reproduction device which is connected by the synchronization control
line 3. At this time, the vertical synchronization signal counter 20
counts the number of generation times of the vertical synchronization
signal inserted between first frames of a video signal which is
reproduced by the reproduction control unit 15 of the second camera 2 as
the frame number of the second processing frames of the second camera 2.
Then, the generation number, which is notified by the second camera 2, of
vertical synchronization signals which are generated by the imaging
element of the second camera 2 and inserted between the second processing
frames is obtained. The number of generation times of the vertical
synchronization signal inserted between the second processing frames is
calculated based on a difference value between the above-mentioned
generation number and the number of generation times of the vertical
synchronization signal inserted between the first processing frames.
Then, based on the number of generation times of the vertical
synchronization signal inserted between the second processing frames, the
second camera 2 is notified of timing on which the second camera 2 starts
an instructed operation after elapse of a predetermined period and
instruction given by operation input. At this time, the first camera 1
notifies the second camera 2 of the timing of start of the operation and
the instruction given by operation input and performs a notified
operation after elapse of the predetermined period from a time point on
which the operation input is performed. The operation instructed by the
operation input of the operation unit 11 includes start or stop of
imaging and the first and second processing frames include an imaging
frame or a reproduction frame.

[0044] FIGS. 3A to 3C are timing diagrams illustrating an example that
operation timing of the second camera 2 is controlled by the first camera
1.

[0045]FIG. 3A illustrates an example of a timing diagram in a state that
synchronization of the first camera 1 and the second camera, 2 is not
controlled.

[0046] The first camera 1 and the second camera 2 use vertical
synchronization signals which are respectively generated at different
timings so as to match start timings, and perform processing of imaging
or reproduction on the basis of a processing frame set within a period
between adjacent vertical synchronization signals. The first camera 1 and
the second camera 2 operates in processing frames of the same frame rate.
However, it is difficult to precisely match timings on which a user
operates the operation unit 11 of respective cameras to power on, and
therefore timings on which processing frames start are different from
each other. Accordingly, if an image of a subject is picked up in a state
that timings of start of processing frames are different from each other
as related art, an operation to match start or stop of processing has to
be performed after the image pick up.

[0047] FIG. 3B illustrates an example of a processing frame of the second
camera 2 which is subject to genlock based on a processing frame of the
first camera 1.

[0048] In this example, such control is performed that start timing of a
processing frame of the second camera 2 is matched with start timing of a
processing frame of the first camera 1, and a vertical synchronization
signal of the first camera 1 is used as a synchronization signal for
matching start timings of processing frames. Genlock is performed with
respect to a processing frame of the second camera 2 by a synchronization
control signal transmitted from the first camera 1 via the
synchronization control line 3. Here, the first camera 1 and the second
camera 2 have the same configuration, so that a processing frame of the
second camera 2 can be used as a synchronization signal to perform
genlock of a processing frame of the first camera 1.

[0049] Here, processing to match start timings of processing frames of the
first camera 1 and the second camera 2 is described.

[0050] First, as soon as a vertical synchronization signal is generated as
first timing of a processing frame, the first camera 1 notifies the
second camera 2 of a counted vertical synchronization signal counter
value via the synchronization control line 3. This vertical
synchronization signal counter value is used as a counter value of a
processing frame.

[0051] In a similar manner, as soon as a vertical synchronization signal
is generated as first timing of a processing frame, the second camera 2
notifies the first camera 1 of a counted vertical synchronization signal
counter value via the synchronization control line 3. In FIG. 3B,
vertical synchronization signal counter values of the first camera 1 are
counted as n, n+1, . . . , and vertical synchronization signal counter
values of the second camera 2 are counted as m, m+1, . . . , for the sake
of convenience of the description.

[0052] The first camera 1 and the second camera 2 mutually notify of
vertical synchronization signal counter values within a period of one
frame. This operation is performed over several frames. Then, the
synchronization control unit 17 of the first camera 1 calculates a
difference value Δ which is obtained by subtracting the vertical
synchronization signal counter value of the second camera 2 which are
obtained for several frames from the vertical synchronization signal
counter value of the first camera 1. In this example, a value is obtained
by a difference value Δ=n-m, and when difference values Δ
calculated over several frames are continuously same values as each
other, the difference value Δ is obtained as an average value.

[0053] Here, as the (m+3)th frame of the second camera 2, there is a case
where a counter value of the (m+3)th frame is not notified within
corresponding (n+3)th frame of the first camera 1 but is notified in the
next (n+4)th frame. For example, there is a case where it is difficult
for the first camera 1 to notify the second camera 2 of the frame number
of the first processing frame within a period of the first processing
frame, or to receive the frame number of the second processing frame from
the second camera 2 within a period of the first processing frame. In
this case, the synchronization control unit 17 of the first camera 1
notifies the second camera 2 of the frame number of a first processing
frame over a frame period following the first processing frame.
Alternatively, the first camera 1 receives the frame number of a second
processing frame from the second camera 2. Accordingly, the first camera
1 and the second camera 2 can mutually securely notify of the frame
numbers of processing frames.

[0054] As shown in FIG. 3B, when the synchronization control unit 17
obtains a second difference value Δ' which is different from the
difference value Δ, which is obtained to be same over predetermined
times or more, over less than predetermined times, the synchronization
control unit 17 discards the second difference value Δ'. In the
example of FIG. 3B, the second difference value Δ' is obtained by
Δ'=(n+4)-(m+3)=n-m+1. Thus, the second difference value Δ'
which suddenly deviates from an average value is discarded. Accordingly,
the synchronization control unit 17 of the first camera 1 can figure out
how much a processing frame of the second camera 2 deviates from a
processing frame of the first camera 1, based on a difference value
Δ.

[0055] FIG. 3C illustrates an example of timing at which the first camera
1 and the second camera 2 actually perform start or stop of processing.

[0056] As shown in FIG. 3B, the synchronization control unit 17 of the
first camera 1 figures out a difference value Δ.

[0057] Here, in FIG. 3C, processing frames of the first camera 1 are
counted as x, x+1, . . . , and processing frames of the second camera 2
are counted as y, y+1, . . . , for the sake of convenience of the
description.

[0058] When start or stop of processing is performed from the (x+5)th
frame, the synchronization control unit 17 gives an instruction to the
second camera 2 to overwrite a counter value of the (x+5-Δ)th frame
on a counter value of the (y+5)th frame. At this time, the
synchronization control unit 17 of the second camera 2 rewrites the
counter value of the (y+5)th frame into the counter value of the
(x+5-Δ)th frame. Accordingly, the first camera 1 and the second
camera 2 perform start or stop of processing at same timing shown by a
star mark in FIG. 3C as a counter value of the same frame.

[0059] A processing example of the synchronization control unit 17 is now
especially described as a processing example of the stereoscopic video
imaging system 10 with reference to FIGS. 4 to 7. Here, in this example,
the synchronization control unit 17 is described because the first camera
1 is set to be a main device. However, even in a case where the second
camera 2 is used as a main device, the second camera 2 can perform
processing same as that of the synchronization control unit 17 described
below.

[0060] FIG. 4 illustrates a processing example of the first camera 1.

[0061] First, when the synchronization control line 3 is connected to the
line terminals of the first camera 1 and the second camera 2, the
synchronization control line mode is turned on by operation input of the
operation unit 11 which is performed by a user with a menu screen which
is not shown (step S1). When the synchronization control line mode is
turned on, imaging processing of a video image or reproducing processing
of a video image can be performed in a synchronized manner between the
first camera 1 and the second camera 2 in processing frames of respective
cameras under a master-servant relationship in which the first camera 1
is set to be a main device and the second camera 2 is set to be a sub
device. On the other hand, when the synchronization control line mode is
turned off, the respective cameras independently operate and therefore do
not mutually influence.

[0062] Next, the first camera 1 and the second camera 2 mutually notify of
vertical synchronization signal counter values via the synchronization
control line 3 by serial communication (step S2). Subsequently, the
synchronization control unit 17 of the first camera 1 detects difference
between the vertical synchronization signal counter value of own device
and the vertical synchronization signal counter value which is received
from the second camera 2. At this time, if the same difference value is
continuously obtained for N frames (in this example, 5 frames), the first
camera 1 determines the difference value (step S3).

[0063] Then, the first camera 1 receives an instruction of start or stop
of processing by an operation signal which is generated in response to an
input operation performed on the operation unit 11. In response to this
instruction, the first camera 1 specifies a counter value of a processing
frame of several frames after in light of communication time used for
instructing the second camera 2, so as to transmit an operation
instruction to the second camera 2 (step S4). The timing diagram shown in
FIG. 3C shows an execution of 5 frames after.

[0064] Thus, the first camera 1 and the second camera 2 perform the same
operation as each other in synchronization with the timing of the
vertical synchronization signals which are generated at the same timing
(step S5). Accordingly, a user can make the second camera 2 perform the
same operation only by operate the first camera 1.

[0065] Next, an example of a processing, which is performed by the
synchronization control unit 17, of an interface with respect to each
unit is described with reference to FIGS. 5 to 7. In the description
below, processing that the synchronization control unit 17 performs
input/output of data with respect to each control unit is called
"processing of an interface".

[0066]FIG. 5 illustrates an example of processing, which is performed by
the synchronization control unit 17, of an interface of the camera
control unit 13.

[0067] First, the synchronization control unit 17 waits interruption of a
vertical synchronization signal which is generated by an imaging element
(step S11). When the interruption of the vertical synchronization signal
occurs, the vertical synchronization signal counter 20 writes a vertical
synchronization signal counter value in the RAM 14. Then, the
synchronization control unit 17 acquires the vertical synchronization
signal counter value from the RAM 14 (step S12).

[0068] The vertical synchronization signal counter value is repeatedly
counted up from "0" to "255" by the vertical synchronization signal
counter 20 after the first camera 1 is powered on. Here, the vertical
synchronization signal counter value at a time point on which the
vertical synchronization signal counter 20 starts counting has a random
value. Further, if synchronization between the first camera 1 and the
second camera 2 is stable, the difference value Δ is a fixed value,
and an absolute value of the vertical synchronization signal counter
value at a time point of starting an operation is calculated every time.
Accordingly, the vertical synchronization signal counter value does not
have to be reset to "0".

[0069] Next, the synchronization control unit 17 transmits the vertical
synchronization signal counter value read out from the RAM 14 to the
second camera 2 (step S13). The processing to transmit the vertical
synchronization signal counter value is performed by a module which
processes an interface of the camera control unit 13. Then, the
synchronization control unit 17 requests transmission from the
transmission/reception control unit 19, and therefore transmission
processing is performed.

[0070] Next, the synchronization control unit 17 determines whether the
vertical synchronization signal counter value of own device is equal to a
vertical synchronization signal counter value at a time point on which
the second camera 2 stars an operation (step S14). When the vertical
synchronization signal counter values are equal to each other, the
synchronization control unit 17 performs reproducing instruction or
recording instruction of a video image with respect to the reproduction
control unit 15 or the record control unit 16 (step S15). When the
vertical synchronization signal counter values are different from each
other, the synchronization control unit 17 does not perform any
processing and ends the processing.

[0071]FIG. 6 illustrates an example of processing, which is performed by
the synchronization control unit 17, of an interface of the user
interface control unit 12.

[0072] First, the synchronization control unit 17 waits an operation
instruction by an operation signal which is generated in response to
operation input of a user (step S21). However, when the operation
instruction from the user is given in a processing frame is indefinite.
Therefore, the synchronization control unit 17 performs genlock in
response to an operation instruction so that vertical synchronization
signals are simultaneously generated between the first camera 1 and the
second camera 2, being able to start the instructed operation from the
beginning of the processing frame which is the timing at which the
vertical synchronization signal is generated.

[0073] Further, the first camera 1 notifies of the operation instruction
which is operate-inputted by the operation unit 11, by transmitting an
operation signal to the second camera 2. Here, the timing when the
operation signal reaches the second camera 2 is indefinite and therefore
when the operation is actually performed is unclear. Therefore, the first
camera 1 and the second camera 2 preliminarily obtain a difference value
Δ from vertical synchronization signal counter values counted by
respective vertical synchronization signal counters 20. With this, a
vertical synchronization signal counter value at which the first camera 1
and the second camera 2 can start an operation in a synchronized manner
is calculated in light of the difference value Δ.

[0074] Then, the synchronization control unit 17 of the first camera 1
calculates a vertical synchronization signal counter value at a time
point on which the second camera 2 starts an operation, based on the
difference value Δ which is determined by the vertical
synchronization signal counter value received from the second camera 2
(step S22). Further, the synchronization control unit 17 of the first
camera 1 calculates a vertical synchronization signal counter value at a
time point on which the first camera 1 starts an operation, in parallel
with the processing of step S22 (step S23).

[0075] A dashed line branched to step S23 on the subsequent step of step
S21 represents processing which is performed when the first camera 1 is
set to be a sub device. This processing is provided because processing to
be performed varies depending on whether a parameter of an operation
instruction received from the operation unit 11 is a counter value of own
device or a counter value of the other device. Subsequently, the
synchronization control unit 17 transmits an operation signal for
performing an operation instruction and the vertical synchronization
signal counter value at a time point on which the operation is started to
the second camera 2 (step S24), and the processing is ended.

[0076] FIG. 7 illustrates an example of processing, which is performed by
the synchronization control unit 17, of an interface of the
transmission/reception control unit 19.

[0077] First, the synchronization control unit 17 of the first camera 1
waits reception of a vertical synchronization signal counter value
received from the transmission/reception control unit 19 (step S31). If
the vertical synchronization signal counter value is not received from
the second camera 2, the processing is ended.

[0078] On the other hand, when the transmission/reception control unit 19
receives the vertical synchronization signal counter value from the
second camera 2 (step S32), the transmission/reception control unit 19
writes the vertical synchronization signal counter value in the RAM 18.
Subsequently, the synchronization control unit 17 acquires the vertical
synchronization signal counter value from the RAM 18 (step S33). Then,
the synchronization control unit 17 calculates a difference value Δ
between a vertical synchronization signal counter value of own device
read from the RAM 14 and the vertical synchronization signal counter
value of the second camera 2 read out from the RAM 18 (step S34).

[0079] The synchronization control unit 17 calculates a difference value
Δ for every frame and the latest difference value Δ is
calculated in step S34. In the following description, the difference that
the synchronization control unit 17 calculates one frame before is a
value which is obtained by a vertical synchronization signal counter
value of one frame before, thereby being called "previous time's
difference". While, the difference value Δ calculated in step S34
is called "this time's difference". Then, the synchronization control
unit 17 determines whether this time's difference is equal to the
previous time's difference (step S35). Subsequently, the synchronization
control unit 17 writes a difference determination counter value, to which
the number is added when this time's difference is equal to the previous
time's difference, in the RAM 14 so as to determine whether difference
values Δ have a constant value over several times (step S36).

[0080] Then, the synchronization control unit 17 determines whether the
difference value Δ is a value enabling an increase of the
difference determination counter value or an abnormal value corresponding
to a second difference value Δ' (step S37). When the difference
value Δ is an abnormal value, the processing is not performed. On
the other hand, when the difference value Δ is a value enabling an
increase of the difference determination counter value, processing of
writing the previous time's difference over a determined difference in
step S38 of subsequent processing.

[0081] In this example, a difference determination counter value is used
so as to determine a difference value Δ of a vertical
synchronization signal counter value. For example, as shown in FIG. 3C
described above, in a case where a communication packet which is
transmitted through the synchronization control line 3 is delayed, this
time's difference may be different from the previous time's difference.
In order to enable discarding of the difference value Δ which is
obtained as this time's difference in such case, such control is
performed that this time's difference is not considered as a correct
difference value Δ in a case where this time's difference and the
previous time's difference do not have the same value N times (five times
in this example) in a row.

[0082] Here, when the difference value Δ varies, the synchronization
control unit 17 once writes the varied difference value Δ in the
RAM 14 as a "previous time's difference". Subsequently, when the same
difference value Δ is obtained, the synchronization control unit 17
increases the difference determination counter value in the RAM 14 by 1.
Further, when this time's difference and the previous time's difference
have the same value continuously, the synchronization control unit 17
continues to increase the difference determination counter value each
time. Thus, in a case where this time's difference and the previous
time's difference have the same value over N frames, a "determined
difference value" represented by the above-described difference value
Δ is obtained (step S38). Further, in a case where this time's
difference and the previous time's difference have the same value for N
times in a row, a value of "N" which is the difference determination
counter value is written over the difference determination counter value
(step S39), and the processing is ended. Here, the value of "N" is
increased every time this time's difference and the previous time's
difference have the same value.

[0083] When this time's difference and the previous time's difference are
different from each other in the processing of step S35, the previous
time's difference written in the RAM 14 is updated by this time's
difference (step S40), and the difference determination counter value is
rewritten by a default value "1" (step S41). Subsequently, the processing
of steps S31 to S39 is repeated so as to obtain whether a value
represented by this time's difference is a determined difference Δ.

[0084] Here, there is a case where the first camera 1 is set to be a sub
device and the second camera 2 is set to be a main device. In this case,
the transmission/reception control unit 19 of the first camera 1 receives
an operation signal from the second camera 2 and the synchronization
control unit 17 of the first camera 1 interprets an operation instructed
by the second camera 2 (step S42). Further, the transmission/reception
control unit 19 of the first camera 1 receives a vertical synchronization
signal counter value at a time point on which an operation is started,
from the second camera 2 (step S43) and writes this vertical
synchronization signal counter value in the RAM 18 of the first camera 1.
Then, the synchronization control unit 17 of the first camera 1
calculates a vertical synchronization signal counter value at a time
point on which an operation of own device is started, based on a
determined difference value (step S44) in parallel with the processing of
step S43 and performs the operation controlled by the second camera 2.

[0085] According to the stereoscopic video imaging system 10 of the
above-described embodiment, a difference value Δ of vertical
synchronization signal counter values is obtained in a state that
generation timings of vertical synchronization signals are mutually
matched by using the first camera 1 and the second camera 2 having the
master-servant relationship. Then, the number of frames in which start of
stop of processing is actually performed is determined in light of this
difference value Δ and thus the start or stop of processing can be
simultaneously performed at a reach of this frame number. At this time,
the second camera 2 performs the same operation as that of the first
camera 1 when a user performs operation input only with respect to the
operation unit 11 of the first camera 1 which is a main device, for
example. Accordingly, start or stop of processing of two cameras can be
precisely controlled in synchronization with a start timing of a
processing frame.

[0086] Further, the start timing of a processing frame is matched with the
generation timing of a vertical synchronization signal of a video signal,
so that operations of respective processing frames can be accurately
matched. Accordingly, an operation to adjust processing frames does not
have to be performed after a subject is imaged, so that an editing
operation becomes more efficient. Further, two cameras can be made
perform a reproduction operation in a synchronized manner in reproduction
of a video image, so that uncomfortable feeling due to mismatched
processing frames with respect to a stereoscopic image can be eliminated.

[0087] Further, difference values Δ are obtained over predetermined
times or more, so that the values have high credibility. Therefore,
processing frames can be easily matched by using the difference value
Δ. Further, a user does not have to think of matching start or stop
of processing because the second camera 2 automatically operates in
synchronization with the first camera 1 only by an operation of the first
camera 1.

[0088] Furthermore, the second difference value Δ' which is obtained
as an abnormal value is discarded, so that the second difference value
Δ' does not affect synchronization control. From this point,
credibility of synchronization control of the first camera 1 and the
second camera 2 can be enhanced.

2. Modification

[0089] In the above-described embodiment, such example that the first
camera 1 and the second camera 2 are disposed in the vertical direction
is described. However, the first camera 1 and the second camera 2 may be
aligned in a horizontal direction by reducing sizes of casings of the
first camera 1 and the second camera 2.

[0090] Further, in the example, the synchronization control line 3 is used
as a wired cable which is connected to the transmission/reception control
unit 19 is described. However, a communication packet may be wirelessly
transmitted by using an adapter compatible with a wireless communication
standard as the transmission/reception control unit 19.

[0091] The series of processing in the embodiment described above may be
performed by either hardware or software. When the series of processing
is performed by software, the processing can be performed by a computer
in which a program constituting the software is incorporated in dedicated
hardware or by a computer in which a program for executing various
functions is installed. For example, the processing may be performed by
installing a program constituting desired software in a general-purpose
personal computer.

[0092] Further, a recording medium in which a program code of software for
realizing a function of the above-described embodiment is recorded may be
provided to a system or an apparatus. Furthermore, it is apparent that
the function is realized by reading out and executing a program code
stored in the recording medium by a computer (or a control device such as
a CPU) of the system or the apparatus.

[0093] Examples of the recording medium for providing the program code in
this case include a flexible disk, a hard disk, an optical disk, a
magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile
memory card, and a ROM.

[0094] The function of the above-described embodiment is realized by
executing the program code read out by the computer. In addition, an OS
operating on the computer or the like performs part or whole of actual
processing based on an instruction of the program code. A case where the
function of the above-described embodiment is realized by the processing
is also included.

[0095] It should be noted that embodiments of the present disclosure are
not limited to the above-described embodiment, and various alterations
and modifications occur within the scope of the present disclosure.

[0096] The present disclosure may have the following configurations.

[0097] (1) An imaging device including

[0098] an operation unit configured to instruct an operation by operation
input,

[0099] an imaging control unit configured to control an operation of an
imaging unit having a first imaging element that outputs a video signal
in a first processing frame for every vertical synchronization signal
that is inserted between first processing frames, by incident light of a
subject incident through a lens,

[0100] a counting unit configured to count a number of generation times of
the vertical synchronization signal generated by the first imaging
element, and

[0101] a control unit that calculates a number of generation times of the
vertical synchronization signal that is inserted between second
processing frames based on a difference value between a number of
generation times, which is notified from the other imaging device, of the
vertical synchronization signal that is generated by a second imaging
element included in the other imaging device, which is connected by a
control line that transmits a control signal, and inserted between the
second processing frames and a number of generation times of the vertical
synchronization signal that is inserted between the first processing
frames, so as to notify the other imaging device of timing at which the
other imaging device starts an instructed operation after elapse of a
predetermined period and an instruction given by the operation input,
based on the number of generation times of the vertical synchronization
signal that is inserted between the second processing frames, and perform
the operation that is notified of after the elapse of the predetermined
period from a time point on which the operation input is performed.

[0102] (2) The imaging device according to (1), in which

[0103] the counting unit counts a number of generation times of the
vertical synchronization signal that is generated by the first imaging
element as a frame number of the first processing frames, and

[0104] the control unit notifies the other imaging device of a frame
number obtained by adding a plurality of frame periods to a frame number
of the second processing frames, which is calculated when a difference
value between a frame number of the second processing frames received
from the other imaging device every time the second imaging element
generates the vertical synchronization signal and a frame number of the
first processing frames is constant for the plurality of frame periods,
as timing at which the other imaging device starts an operation, in a
case where timing on which a vertical synchronization signal of the first
processing frame is generated and timing on which a vertical
synchronization signal of the second processing frame is generated are
preliminarily matched with each other and the other imaging device counts
the number of generation times of the vertical synchronization signal
inserted between the second processing frames as the frame number of the
second processing frames.

[0105] (3) The imaging device according to (1) or (2), in which when it is
difficult for the control unit to notify the other imaging device of the
frame number of the first processing frames within a period of the first
processing frame or to receive the frame number of the second processing
frames from the other imaging device within the period of the first
processing frame, the control unit notifies the other imaging device of
the frame number of the first processing frames or receives the frame
number of the second processing frames from the other imaging device over
a frame period following the first processing frame.

[0106] (4) The imaging device according to any one of (1) to (3), in which
when the control unit obtains a second difference value, which is
different from the difference value obtained over predetermined times or
more, over less than the predetermined times, the control unit discards
the second difference value.

[0107] (5) The imaging device according to any one of (1) to (3), in which
an operation instructed by the operation input of the operation unit
includes one of start and stop of imaging and the first and second
processing frames include one of an imaging frame and a reproduction
frame.

[0108] (6) A synchronization control method including

[0109] instructing an operation by operation input,

[0110] controlling an operation of an imaging unit having a first imaging
element that outputs a video signal in a first processing frame for every
vertical synchronization signal that is inserted between first processing
frames, by incident light of a subject incident through a lens,

[0111] counting a number of generation times of the vertical
synchronization signal generated by the first imaging element, and

[0112] calculating a number of generation times of the vertical
synchronization signal that is inserted between second processing frames
based on a difference value between a number of generation times, which
is notified from the other imaging device, of the vertical
synchronization signal that is generated by a second imaging element
included in the other imaging device, which is connected by a control
line that transmits a control signal, and inserted between the second
processing frames and a number of generation times of the vertical
synchronization signal that is inserted between the first processing
frames, so as to notify the other imaging device of timing at which the
other imaging device starts an instructed operation after elapse of a
predetermined period and an instruction given by the operation input,
based on the number of generation times of the vertical synchronization
signal that is inserted between the second processing frames, and perform
the operation that is notified of after the elapse of the predetermined
period from a time point on which the operation input is performed.

[0113] (7) A reproduction device including

[0114] an operation unit configured to instruct an operation by operation
input,

[0115] a counting unit configured to count a number of generation times of
a vertical synchronization signal that is inserted between first
processing frames of a video signal that is read out from a recording
unit and reproduced, and

[0116] a control unit that calculates a number of generation times of the
vertical synchronization signal that is inserted between second
processing frames based on a difference value between a number of
generation times, which is notified from the other reproduction device,
of the vertical synchronization signal that is generated by an imaging
element included in the other reproduction device, which is connected by
a control line that transmits a control signal, and inserted between the
second processing frames and a number of generation times of the vertical
synchronization signal that is inserted between the first processing
frame, so as to notify the other reproduction device of timing at which
the other reproduction device-starts an instructed operation after elapse
of a predetermined period and an instruction given by the operation
input, based on the number of generation times of the vertical
synchronization signal that is inserted between the second processing
frames, and perform the operation that is notified of after the elapse of
the predetermined period from a time point on which the operation input
is performed.

[0117] (8) A stereoscopic video imaging system including

[0118] a first imaging device and

[0119] a second imaging device; and

[0120] the first imaging device includes [0121] a first operation unit
configured to instruct an operation by operation input, [0122] a first
imaging control unit configured to control an operation of an imaging
unit having a first imaging element that outputs a video signal in a
first processing frame for every vertical synchronization signal that is
inserted between first processing frames, by incident light of a subject
incident through a lens, [0123] a first counting unit configured to count
a number of generation times of the vertical synchronization signal
generated by the first imaging element, and [0124] a first control unit
that calculates a number of generation times of the vertical
synchronization signal that is inserted between second processing frames
based on a difference value between a number of generation times, which
is notified from the second imaging device, of the vertical
synchronization signal that is generated by a second imaging element
included in the second imaging device, which is connected by a control
line that transmits a control signal, and inserted between the second
processing frames and a number of generation times of the vertical
synchronization signal that is inserted between the first processing
frames, so as to notify the second imaging device of timing at which the
second imaging device starts an instructed operation after elapse of a
predetermined period and an instruction given by the operation input,
based on the number of generation times of the vertical synchronization
signal that is inserted between the second processing frames, and perform
the operation that is notified of after the elapse of the predetermined
period from a time point on which the operation input is performed; and

[0125] the second imaging device includes [0126] a second imaging
control unit configured to control an operation of a second imaging unit
having a second imaging element that outputs a video signal in a second
processing frame for every vertical synchronization signal that is
inserted between second processing frames, by incident light of a subject
incident through a lens, [0127] a second counting unit configured to
count a number of generation times of the vertical synchronization signal
generated by the second imaging element, and [0128] a second control unit
configured to notify the first imaging device of the number of generation
times of the vertical synchronization signal inserted between the second
processing frames and perform an instructed operation after elapse of a
predetermined period from a time point on which the operation input is
performed, based on timing which is received from the first imaging
device and on which the instructed operation is started after the elapse
of the predetermined period and an instruction given by the operation
input and received from the first imaging device.

[0129] The present disclosure contains subject matter related to that
disclosed in Japanese Priority Patent Application JP 2011-066254 filed in
the Japan Patent Office on Mar. 24, 2011, the entire contents of which
are hereby incorporated by reference.